1. Field of the Invention
This invention relates generally to medical appliances; and more particularly to a device for inserting a cannula--such as an intravenous cannula--into a patient's body.
2. Prior Art
As is well known, there are myriad very important medical uses for intravenous and intraarterial tubes and other indwelling catheters. It is also known in the medical community that a severe problem has developed in relation to all such devices.
That problem arises from the continuing presence of horrible diseases, particularly fatal and currently incurable diseases such as acquired immune deficiency syndrome ("AIDS") and hepatitis, transmitted by exchange of body substances between people. These diseases have led medical institutions to exclusively use disposable needles for injections and for catheter or cannula implants.
A severe residual risk remains, however, for medical personnel themselves in the inadvertent touching of needle tips after withdrawal from infected patients. Medical needles are designed and manufactured specifically to be extremely sharp and to puncture skin and flesh with only the slightest pressure.
As a result, what would ordinarily be an inconsequential scratch or pinprick can bring and has brought severe disease or even death to many medical staff members and others. Needless to say, health-care professionals are well aware of this risk and take considerable precautions to avoid such inadvertent punctures; thus the risk is reduced on a "probability" basis to an exceedingly small value.
Nevertheless, the exposure is so massive for working doctors, nurses and technicians that occasional punctures are inevitable. As a practical matter, it is virtually impossible for such an individual to reduce the incidence of accidental puncture to less than, say, one every year or perhaps one every few years.
Of course, not every such puncture follows contamination of the needle by a patient carrying a transmissible fatal disease. Nevertheless, there are enough medical personnel and enough such patients that a significant number of medical staffers die--and of course a greater number become very sick--from these accidents.
In discussion of this problem, needles of the types used with syringes commonly come to prominence. Though the word "hypodermic" has somewhat passed out of current usage in the medical profession, I shall for purposes of definiteness and simplicity refer to needles used with syringes for giving injections as "hypodermic needles." Needles used in drawing blood will be called "phlebotomy needles." By this terminology I mean to clearly distinguish all such needles from needles that are used for cannula insertion, the field of the present invention.
Hypodermic and phlebotomy needles are prominent in discussion because they are used so conspicuously and in such enormous quantity. Interestingly, however, the actual manual manipulations involved in using hypodermic and phlebotomy needles are relatively favorable to avoiding puncture accidents.
More specifically: after a hypodermic needle is withdrawn from a patient, the person using the needle in some circumstances (e.g., intramuscular injections) immediately has both hands available to properly deal with the needle. In normal circumstances he or she can promptly sheath and discard it before further tending to the patient.
In many other situations (e.g., intravenous injection) the person using the hypodermic needle almost always has one hand free to at least hold the needle until it can be properly sheathed. In some situations that are more demanding of dexterity (e.g., blood withdrawal), the person using the phlebotomy needle usually can at least find a second to place it temporarily well out of the way until there is time for safe disposal.
(It will be understood that my discussion here is directed to the relatively lower danger in procedures for injections or blood withdrawal, as contrasted with the procedures for cannula insertion. Thus I do not mean to imply that once properly sheathed, hypodermic needles used for intramuscular injections are necessarily safe: there of course remains a certain amount of potential for inadvertent unsheathing and many other kinds of accidents.)
Of course there are exceptions to the foregoing general proposition that injection and phlebotomy procedures are relatively less dangerous than cannula-insertion procedures. There are learning situations and emergencies, and circumstances in which the usual manipulations are complicated by patient mental or physical condition. These are, however, probably only between ten and twenty percent of all instances of use of hypodermic and phlebotomy needles.
Procedures for insertion of intravenous or other cannulae are not so favorable for avoidance of accidental punctures. When a cannula has been emplaced in a patient's blood vessel, for example, the cannula potentially forms an open channel for conveyance of the patient's blood to the outside of the body.
The patient's blood vessel must therefore be blocked firmly until and while this channel is connected to a mating tube--which is pressurized, typically with fluid to be infused into the patient's body. In practice the doctor, nurse or technician usually blocks the blood vessel by pressing manually on the outside of the patient's body, just at the tip of the cannula.
This pressure is maintained continuously until the tube is attached to the cannula. From this it will be understood that, before the medical staff member will have both hands free, there will be an intermediate time during which neither hand is free.
In some instances the needle used to emplace the cannula is hollow, and the tubing can be temporarily connected to the back of that needle. This is in fact only temporary relief, however, since eventually the tubing must be removed from the needle, the needle removed from the patient, and the tube reconnected to the cannula.
In some cases the person using the needle is able to place nearby, in advance, a tray in which to temporarily deposit the unsheathed needle without moving out of arm's reach of the patient. This option is not always available, however, and in any event using such a tray is itself a risky proposition.
As a result, a medical staff member who frequently start intravenous tubes and the like typically becomes adept at sheathing needles with one hand. Heretofore this has been the least problematical solution to a continuing problem.
It is nevertheless a very poor solution. It is precisely the kind of maneuver that sooner or later goes astray, leading to an occasional scratch or puncture and thereby statistically to severe illness or death.
FIG. 16 shows a device generally representative of present-day standard, commercially available cannula insertion kits. The familiar term in the health-care professions for such a prior-art device is "I. V. insertion set"--the initials standing for the word "intravenous."
The needle is stainless steel and extremely sharp at its frontal end, which is the left end as drawn in FIG. 16. The shank of the needle is permanently secured into the frontal end of a molded plastic cylinder, with the sharp end of the needle projecting forward out from the cylinder as illustrated. The cylinder may be typically made of polycarbonate.
For reasons that will shortly appear, the needle is preferably but not necessarily hollow. I am not familiar with the manufacturing details of these articles, but it would appear that the needle may be secured to the cylinder by a press fit or shrink fit, or by molding the plastic cylinder in place on the needle.
A separate catheter assembly or "cannula" fits very snugly, but removably, onto the forwardly projecting part of the needle. The tapered front of the cannula slides with the needle through a patient's skin and flesh.
The rear portion or hub of the cannula is radially enlarged and formed to define a very slightly tapered rearward receptacle for a standard-diameter tube, such as intravenous supply tubing. The cannula, or at least its part that is fitted snugly onto the shank of the needle, is of a biologically inert but very slippery material, such as that available commercially under the well-known trade name "Teflon." The hub is typically of high-molecular-weight polypropylene or the like.
In use the needle and cannula are inserted together into a patient's blood vessel--or in some cases into a body cavity, or an abscess, or wherever fluid communication is to be established. As previously mentioned, the medical staff person using the device then usually applies pressure to the outside of the patient's body just ahead of the needle tip, to prevent outward flow of blood.
The medical staff member then withdraws the needle, leaving the cannula in place within the body. Finally the fluid communication is completed by insertion of a standard-diameter tube into the receptacle at the rear end of the cannula.
In a typical cannula insertion set the rearward portion of the cylinder is formed very similarly to the rear end of the cannula, making allowance for the difference in properties of the cylinder and cannula materials. This shaping permits attachment of the standard tubing to the cylinder rather than the cannula.
In use, when it is not necessary or desirable to leave the cannula alone in the patient's body with the tubulation attached--or if it is not desirable to do so immediately--an intravenous or like connection can be made through the steel needle. It is for this reason that the needle is advantageously hollow.
A separate safety cover (not illustrated) is typically supplied in place on each insertion set. The separate safety cover firmly grips the cylinder and entirely covers the needle, to prevent accidental puncture and to prevent accidental contamination of the needle by substances in the environment, before use.
To use the insertion set, the safety cover must be entirely removed and set aside.
As already outlined, our focus of concern now shifts to the possibility that the needle may be contaminated by substances in the patient, during use. Accordingly the safety cover is to be replaced over the sharp end of the needle to prevent accidental puncture and, particularly, to prevent contact of people other than the patient, with possible contaminants on the needle.
It is here that the prior art fails to be effective, since the process of replacing the safety cover is subject to the risks previously described. As far as I know, the medical marketplace lacks any appliance or apparatus aimed at solving this problem.
The closest safety device that may be at all relevant is actually in a different field, namely the field of hypodermic needles. That device is a special form of hypodermic needle, available commercially from the firm ICU Medical, Inc. under the trade name "ICU High Risk Needle."
The ICU device is fitted with a sliding sheath that is carried on the shaft of the hypodermic needle itself. After use the sheath is advanced forward over the needle tip.
This device undoubtedly serves a useful purpose, and it is certainly not my desire to criticize what is apparently the only commercial effort directed to problems even remotely analogous to those of interest here. On the other hand, that device evidently has limitations that should be mentioned.
First, the ICU High Risk Needle is offered as a special item at a special price, for use only with patients known to be "high risk" patients. Not all patients carrying transmissible fatal diseases are known to be high risks.
Secondly, the sheath is attached halfway out the needle, where there would appear to be potential for inadvertent application of lateral force with sufficient leverage to snap off the needle. If that should occur before the sheath were fully advanced, the potential for accidental puncture could be substantial.
Thirdly, it is not clear from commercial literature on the product that the sheath locks in place when advanced--or, if so, that it locks firmly enough to withstand normal jarring in the workplace. Without such a feature, the device would seem to offer very limited protection.
Finally, as already suggested, the ICU product is neither designed nor offered for use in insertion of cannulae or the like. It appears to require substantial modification for any such use.
A number of patents have been issued for devices that shield medical needles, but they are virtually all for hypodermic or phlebotomy needles. Only one of these patents even mentions needles used in emplacing intravenous cannulae. That is U.S. Pat. No. 4,592,744, issued June 3, 1986, to Janine C. Jagger et al. The introductory passages of the Jagger patent refers to, e.g.
safety venipuncture devices having needle retracting means, particularly hypodermic needles having a retractable needle, vacuum tube phlebotomy systems having retractable needles, and intravenous devices having retractable needles.
Once past the introductory portions of the patent, however, Jagger et al. confine their disclosure to hypodermic and phlebotomal uses. They never again mention any possibility of applying their invention to intravenous devices.
In other words, although the Jagger patent represents that it encompasses disclosures within the field of the present invention, that does not appear to be so. The Jagger disclosure fails to include any specific disclosure directed to safely inserting a cannula into a patient.
Jagger et al. do illustrate and describe a device that facilitates retraction of a hypodermic needle into a personnel-protective enclosure. They also show and describe another device that similarly facilitates retraction of a phlebotomy needle into a like enclosure. In both of these devices the retraction procedure is relatively cumbersome.
In the hypodermic device, the needle is mounted by a relatively tight press fit to the forward end of a syringe that is fitted within the handle. The needle also extends in a relatively loose press fit through a hole in the front of the handle.
After use, the syringe must be pulled bodily out of the back end of the handle, carrying the needle rearward out of its front-end press fit with the handle, and into the cavity within the handle. The needle is carried in a flange that is too wide to escape from the rear end of the handle, and accordingly is pulled away from its tight press fit to the front end of the syringe. It is thus trapped within the handle.
In the phlebotomy device, the blood-collection receptacle is initially enclosed within an outer housing/handle during use. The rear end of the needle passes in a tight friction fit through an elastomeric stopper on the receptacle.
Thereafter the receptacle is used as a tool to unscrew the needle from the forward end of the handle. Then the receptacle stopper is pulled off the rear end of the needle, so that the receptacle with its blood sample can be removed from the handle. As the receptacle is withdrawn, the needle is trapped by its flange in the handle.
Thus the two forms of the Jagger invention that are described require the user to actually pull the needle all the way back through the hole in the handle. This motion must be continued until the needle is entirely within the handle cavity.
It will be seen immediately that for a needle more than about an inch long this manipulation is difficult to accomplish using only one hand. The difficulty will be compounded if the maneuver must be performed with only part of the user's attention, as is often the case.
In most instances the necessary manual operations must include several motions in sequence. What is required is a compound motion, each stage of which is typically of relatively large amplitude in comparison with the length of the needle and the size of the user's hand.
As a matter of ergonomics, the requirement for such large-amplitude and compound motions is inherently adverse to definite, reliable and therefore safe retraction. This is particularly so for medical personnel under harried circumstances.
Other factors, specific to the hypodermic and phlebotomy applications of the Jagger invention, make the procedure even more awkward and difficult. First, as to the Jagger hypodermic needle, proper retraction depends upon maintenance of the design relationships between two friction levels. These relations are too easily upset.
For example, they can be disturbed by temperature variations in storage, beyond the knowledge of the person using the device. They can also be disturbed by leakage of congealable or sticky substances such as blood or sucrose solution, through the large opening at the rear of the handle and into the exposed seams between the handle and the needle flange.
The necessary friction relationships can also be disturbed by imperfect insertion of the syringe tip into its mating receptacle at the rear of the needle flange. That procedure, which in many cases is performed by medical technicians on site, rather than the manufacturer's personnel, can at least in principle damage either of the friction-fitting surfaces involved.
In such circumstances the syringe can be extracted from the needle flange before the needle is retracted--leaving no proper means for retraction.
As to the Jagger phlebotomy needle, the arrangement for retraction is even more adverse to reliable operation. The flange of the phlebotomy needle must actually be unscrewed before it can be pulled back into the handle.
In any event, it is not suggested how the Jagger invention might be configured or might function for use in a cannula insertion device. As previously mentioned, that is the field of the present invention.
Other prior patents describe devices for automatic or semiautomatic resheathing of hypodermic syringes. These, however, do not even mention the possibility of intravenous-cannula use.
U.S. Pat. No. 4,026,287 to Haller is among the better of these, since it at least provides for retraction of the used needle into a cavity in a unitary, sturdy structure. The Haller device, however, requires screwing the syringe plunger into the back of the needle flange after use, to destroy a frangible seal around the flange and then retract the needle.
Haller also fails to protect against inadvertent insertion of fingertips into the syringe barrel. Even more serious is the fact that Haller's syringe plunger can remain in place, held only by detents at the rear of the barrel.
The Haller plunger thus remains dangerously ready to drive the needle forward again if the syringe is accidentally jarred past the detents. In addition, Haller's device and most of the others discussed below are disadvantageous in that their after-use sheathing configurations are at least as long as--or in some cases longer than--the initial or before-use configurations.
A device to be discarded, particularly one that is dangerous if broken open, should not be so extended and should not have a multiple-stage structure. Such configurations invite breakage and potentially serious accident.
(It should be noted in passing that in the present context the title of Haller's patent may be somewhat misleading. That title is "Syringe with Retractable Cannula"--her term "cannula," however, does not refer to an indwelling-catheter cannula, but simply to the forward end of the syringe body.)
U.S. Pat. No. 4,631,057 to Mitchell also leaves the needle accessible to fingertips through the unsealed forward end of the sheath. Mitchell's device also shares with the Haller device an undesirable sensitivity to jarring the device out of its safety detents, and in addition a similar undesirable extended after-use configuration.
Other patented devices with a like vulnerability to jarring out of detents and a like extended postuse configuration, but at least providing better frontal shielding against fingertip insertion, are U.S. Pat. Nos. 4,573,976 (Sampson), 4,643,199 (Jennings, Jr. et al.) and 4,643,200 (Jennings, Jr.).
Worthy of mention for its provision of more positive resistance to jarring of the needle out of retracted position is U.S. Pat. No. 4,425,120 to Sampson et al. That device pays for its better safety locking with complexity of the manual manipulations required in use.
Similar observations apply to U.S. Pat. No. 3,890,971 to Leeson, which offers a relatively very compact and stable postuse configuration, but at the cost of a relatively complicated mechanism and large-amplitude motions to effect the resheathing.
Numerous devices for providing merely visual shielding or screening of hypodermic syringes have also been patented. Among these are U.S. Pat. Nos. 2,876,770 (White), 2,674,246 (Bower) and 3,134,380 (Armao). Such devices are actually counterproductive with respect to present purposes, since they effectively conceal the presence of a dangerously sharp and possibly contaminated needle.
Thus the prior art has failed to provide a suitable safety device for use under modern conditions in the field of the present invention--medical indwelling-cannula insertion. No prior-art device adequately protects people from contact with portions of the device that have been within the patient. In particular, no prior-art device provides the necessary sure and easy operation that is essential to the effectiveness of such protection.